


a Crack in the Wall

by BloomingMiracle (Luna264)



Category: Death Note (Anime & Manga)
Genre: Gen, POV Yagami Sayu, Yagami Sayu Knows
Language: English
Status: Completed
Published: 2021-02-22
Updated: 2021-02-22
Packaged: 2021-03-11 23:53:47
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 1
Words: 2,792
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29625924
Author URL: https://archiveofourown.org/users/Luna264/pseuds/BloomingMiracle
Summary: The culprit, she was pretty sure, was a small crack by the intersection of their shared wall and the wall with her nice, big window in it. She liked that window. She’d filled jars and bottles with water and dish soap and glitter and lined them up so the light could shine through them and make a rainbow next to her door. She’d been planning to ask her parents to have the crack sealed, because sometimes her brother stayed up too late working on who knew what that was loud enough to keep her up, too.That was before Light had become Kira, though.
Relationships: Yagami Light & Yagami Sayu, Yagami Sachiko & Yagami Sayu, Yagami Sayu & Yagami Souichirou
Comments: 2
Kudos: 20





	a Crack in the Wall

Sayu Yagami turned the volume up on the music in her headphones and sighed. If Light didn’t stop monologuing in the next ten minutes she was going to interrupt him with her math homework again, she _swore._

He liked to think she couldn’t hear him, because he never heard her when she was doing her own thing in her room, but that was because Sayu tried to be quiet enough not to be a bother through the wall, because she was _polite,_ damnit. More than a few times, she’d wished he was right.

The culprit, she was pretty sure, was a small crack by the intersection of their shared wall and the wall with her nice, big window in it. She liked that window. She’d filled jars and bottles with water and dish soap and glitter and lined them up so the light could shine through them and make a rainbow next to her door. She’d been planning to ask her parents to have the crack sealed, because sometimes her brother stayed up too late working on who knew what that was loud enough to keep her up, too.

That was before Light had become Kira, though.

Oh, she pretended she didn’t know. It was the best idea she could come up with. She heard him through the crack in the wall, kill the man that was meant to be L, and laugh.

He was her big brother, yes. But this “death note” had brought out a ruthlessness in him previously reserved solely for family board game nights.

She couldn’t admit the crack was there.

She couldn’t admit that she could hear him.

She looked at her clock, and paused her music. He was still going. She sighed, taking her headphones off and starting to gather up her stuff to give him something _normal_ to focus on for a few minutes.

Then the call came from downstairs. “Kids! Dinner!”

Alright. Later, then. She set her stack of papers aside and went downstairs. Light would join them shortly-- he wouldn’t risk acting abnormal where he knew someone would know.

* * *

Dad came home that night. He was on the Kira case, dedicated to unmasking his own son, not that he knew that part.

“I don’t like that look on your face,” Light said, despite the fact that Sayu knew he was probably _very_ satisfied with himself and drafting up another two hour monologue where he’d pretend he had someone to talk to about the whole serial murder thing. “Still no luck with the investigation?”

“Nothing,” Dad sighed. “But I shouldn’t burden you all with all this, should I? Let’s talk about something else.”

“Yes, let’s,” Mom agreed. “Kids, why don’t you tell your father how school is going?”

“School’s going great,” Light said, and took a particularly yummy looking dumpling that Sayu had had her eyes on.

“I hate Kira,” she muttered, just loud enough for him to hear.

“Sayu, Dad doesn’t want to talk about the investigation anymore,” Light said.

“Yes, Sayu, how’s _your_ schooling going?” Dad prompted.

“Mostly good,” Sayu said. “Light’s been helping me with my homework sometimes.”

Dad smiled. “That’s good,” he said. “What a good big brother you have.”

“Yeah,” Sayu said, trying not to think about the ever increasing death count that Light was responsible for. Was she letting this happen, by not saying anything?

Mom and Light smiled, too. Light thought he was getting away with this, that nothing was wrong, that no one knew anything.

* * *

Sayu noticed when Light became suddenly agitated by something, but she pretended she didn't. He wouldn’t realize-- He thinks he’s so much smarter and better than her, after all.

She sat quietly in her room, music playing softly in her headphones around her neck, and did her work.

Light was quiet, too.

Now, him being Kira, Sayu was reasonably sure her brother had developed some sort of paranoia. She didn’t think it’d take much to convince him he was being watched, or listened to. It’d happened a few times already, but in his defense he _had_ been right. In his room, though, so far, he’d thought himself safely alone. Not anymore.

Had he discovered the crack in the wall?

The thought sent a shiver up Sayu’s spine, and her shoulders tensed involuntarily.

What if he was going to kill her?

She shook her head, to herself, and kept working. It was probably just the stress of studying for entrance exams. Kira or not, her brother was a perfectionist when it comes to anything school related.

And if he _was_ going to kill her, there wasn’t really anything she could do about it, anyways.

* * *

Light calmed down after exams were done.

“Calmed down” being a relative term, of course, him being Kira. Sayu heard him do his monologues in his room again.

In her own room, she breathed a quiet sigh of relief. He hadn’t discovered the crack in the wall, after all. She was safe, for now.

He joked with her and Mom at dinner like nothing had ever been wrong.

Maybe it had just been exam stress after all.

* * *

Dad looked so weak in the hospital bed.

He’d had a heart attack. Stress, the doctors said, but Sayu wasn’t sure. She and Mom were with him, since he was allowed to have two visitors at a time, each holding one of his hands.

She wanted to ask him if he’d moved forward, at all, in the last week or so, but she knew Mom would scold her for bringing up the case when he’d collapsed from the stress of all of it.

But Kira-- _Light--_ was killing people with heart attacks.

If this was his fault…

Sayu shook her head, to herself, and pressed her father’s hand to her forehead.

“I’ll be okay,” Dad said, but his words seemed hollow to her. “I’m not dying until I find the real Kira.”

The real… they had a suspect. Even if that suspect _wasn’t_ Light, that was more confidence than he’d want them to have, she was sure. She shook her head again.

One of the doctors came in, then, and told them that Light and one of the people from the Task Force were there, and wanted to see Dad.

Sayu and Mom left the hospital room, but Sayu would have been lying if she’d said she’d been dignified about it.

They sat in a waiting area for a while.

After a while, a man who couldn’t have been _that_ much older than Light approached them, and told them that one of them could go back and join Light with Dad.

Sayu let Mom go. She didn’t want to see her brother just then.

The man didn’t leave, taking up a position on the other end of the bench. “Tell me about your brother,” he said without preamble.

“Um,” Sayu said. What else could she say? She couldn’t just tell this _stranger_ that her brother was Kira. What if he knew? What if they were accomplices? Light _did_ have a phone, and some of his monologues sounded like he might think someone was listening and answering. He even had a name for that someone-- someone Sayu had never heard. Ryuk, or something. “Who-- Who are you?”

“I’m on the Task Force, with your father,” the man said. She couldn’t get a good read on him. Some people were like that. “He talks about your brother a lot. I just wanted to know what _you_ thought of him.”

“Okay, but,” she said, “who are you?”

“Hideki Ryuga,” the man said.

It was a fake name. Of course it was. But it was close enough to “Ryuk” that Sayu’s breath caught in her throat.

She couldn’t let this man know what she knew. He might be “Ryuk”. He might tell Light.

“Okay, Mr. Ryuga,” she said instead. Let him think she believed him. Trusted him. “Um, Light’s a good big brother. He helps me with my homework when I ask him to, and when I was little he’d comfort me when I had a nightmare. We get along well, even if he takes all the apples in the house before I can get any.”

“I see,” the man said after a few moments, as if what she’d said was any help to him at all. “Thank you.”

This man _knew_ Light was Kira. He _had_ to. And he’d come to visit Dad in the hospital with him, like he _cared._

* * *

Sayu listened to the broadcast through the crack in the wall, as well as Light’s response to it.

Another Kira.

Light was talking to Ryuk-- Ryuga-- it must have been a fake name, in case anyone managed to get their hands on the conversations somehow-- about it, immediately. Sayu didn’t care what he thought of the other Kira-- any judgements he had would be hypocritical, anyways.

After that, Light joined Dad on the Task Force.

That _was_ weird. She’d assumed Ryuga was monitoring the Task Force for him already. Maybe Light had decided that anything he wanted done well, he’d have to do himself. That seemed like him.

* * *

Light responded to the other Kira. The other Kira responded to Light.

Sayu did her literature homework downstairs, and figured that either Light was too overconfident for his own good and was going to get himself caught, or she’d assumed everything was more obvious than it actually was, seeing as she already had all the answers from the crack in the wall.

There was a knock at the door.

Mom got it.

There was a _model_ there. Sayu had seen her, in magazines sometimes. Mom didn’t seem to register what was going on; when the model said she had Light’s notebook, she called Light right down, and referred to her as “a young lady”.

The model smiled at Sayu’s blatant gaping, before following Light up to his room.

“Mom,” Sayu said. “Can I use the computer? I need to look some stuff up."

“Of course, sweetheart,” Mom said.

Sayu ran upstairs and looked up various models. She found what she was looking for soon enough; the woman in her house was Misa Amane, an up and coming model who had voiced support for Kira.

Because of course she had.

Sayu deleted her searches on Misa from the computer’s history, and searched some things vaguely related to her assignment. Their parents probably wouldn’t check, but Light might.

* * *

Misa Amane was arrested soon after. Sayu didn’t hear what for, but she had her guesses.

Soon after, Light was detained, too. Dad muttered some disparaging things about a “Ryuzaki” who was probably the Ryuga Sayu had met at the hospital, but he didn’t elaborate when Sayu needled him as to why Light was gone.

Sayu sat in her room, quietly, and wondered if he was gone forever.

It was quiet. Empty.

But not constantly checking her every breath, in case it was somehow too loud and alerted Light to the fact that she might be able to hear him, after all.

She considered asking her parents to do something about the crack in the wall, but at this point if Light came back she wanted to have some sort of warning of what he was going to do next.

* * *

Light was Kira.

But when he came home, after his detainment, he was L, too.

His own worst enemy.

Sayu would have laughed, if he wouldn’t have heard her.

* * *

It was five years later, and Sayu had been kidnapped by the mafia.

The mafia. The fucking mafia.

She half suspected Light of doing this-- of luring her into a false sense of security and then writing such a convoluted death into his notebook that no one else would ever suspect him.

“Why me?” Sayu asked a man who was dressed differently from the surrounding mafia.

“Your father is the Director of the NPA,” the man said. “Hardly a better target, really. I get the notebook, I kill Kira, you go home, theoretically.”

“Do you even know who he is?” Sayu asked, confident he did not.

“I can find out,” the man said. “Easier, once I have his notebook instead of him.”

The man was trying to convince Sayu that the notebook was mundane, as if she hadn’t lived in the room next door to it and heard her brother talk about it because he thought she couldn’t hear for over half a decade.

But she had. He wanted Kira’s notebook, so he wanted Light’s death note, whether he knew it or not.

“If you’re sure,” Sayu sighed.

* * *

Dad was dead.

Sayu was free, but at what cost?

She went home.

* * *

The phone rang.

Mom was in a worse state than Sayu was, so Sayu picked up. “Yagami residence,” she said dully. “Sayu speaking.”

“Just who I wanted to talk to,” the voice on the other end said. A chill ran up her spine.

“Who are you?”

“Call me N,” the voice said. “I’ve been going through my predecessor’s notes, and I saw some idle speculation that caught my attention.”

“Your-- The original L.”

“Yes,” N said. “I suppose it’s impossible to know for _sure_ how much you know simply by living with two members of the Task Force, but you _do_ seem to know quite a bit.”

Sayu considered this for a long moment. “Light talks to himself,” she said finally. “When he thinks he’s alone. There’s been a crack in our shared wall for years. He never knew.”

“I see,” N said. “And you’ve kept everything you’ve learned from that to yourself, all this time?”

“Hardly had a choice,” Sayu said. “If you’d heard some of those things…”

“Mhm,” N said. “So he _is_ Kira, then.”

A pit formed in Sayu’s stomach. “Yeah,” she said, voice tight. “He is. Don’t use my testimony though, please--”

“That will not be necessary,” N said. “L’s notes said you were afraid. Of him _and_ your brother.”

“I… met L?”

“He introduced himself as Ryuga, I believe.”

“Oh,” Sayu said. “I… Light occasionally called someone Ryuk. I thought…”

“Ah,” N said. “I see.”

“What are you going to do now?” Sayu asked, almost in spite of herself.

“Try to help you, I suppose,” N said. “Although, I might need you to help me do that.”

“I can’t,” she said.

“I’m not asking for much,” N said. “I just need you to meet an associate of mine somewhere, and transport something for me. Can you do that?”

Sayu gulped. “Yeah, I can do that.”

* * *

On a train between prefectures, Sayu took up the position N’s associate had coached her in, next to a man named Teru Mikami. She’d seen him on the television, a couple of times.

He admired her brother. Like, a lot.

N’s associate had told Sayu that Mikami almost certainly had the death note-- they’d confiscated a fake from him already, but intercepted communications made it seem likely he still had the real one.

Another perfect forgery sat in Sayu’s bag, which bumped against Mikami’s as the train rumbled out of the station.

Sayu took a deep, quiet breath, closed her eyes, and reached down. Carefully, she swapped the notebook in her bag with the one in Mikami’s.

“Sayu Yagami,” a voice said.

She opened her eyes, and found herself staring right into those of a monster. A Shinigami. N’s associate had warned her.

Success, then.

Hand barely shaking, she reached into her bag and pulled out a cellphone. She stared the Shinigami dead in the eyes as she dialled, held it up to her ear, and listened to the minimum volume voice tell her that the number she’d called was not in service.

“Right, that’s me,” she said.

“Clever girl,” the Shinigami said.

  
“Thank you,” she said. “You’re a friend of my brother, right?”

“An associate,” the Shinigami allowed. “What, you found him out and wanted to continue his legacy.”

“Oh, no, thank you,” she said. “I’m not really interested in that.”

“Then why steal my notebook?” The Shinigami stared at her with unblinking eyes.

The train pulled into the next station, and she got off the train. “I have a prior arrangement,” she said. “I prefer to keep my promises, too.”

“A prior arrangement?” The Shinigami sounded amused.

“Yup,” she said.

“And what would _that_ be?”

“You’ll see,” she said. “If you’re not his friend, I don’t see why you should object, though.”

“It might mean an end to my fun,” the Shinigami said.

“Don’t tell me you haven’t been waiting to watch him fail since the day you met.”

The Shinigami inclined his head. “Fair enough. Hey, how long have you known he was Kira?”

“A while,” she said. “You see, Ryuk, there was a crack in our shared wall. I heard every word.”

The Shinigami laughed.

**Author's Note:**

> Light is a dumb asshole and I like him so much but he CANNOT keep a secret idk HOW it works out for him in canon L narrows it down SO fast


End file.
